NL115 Ethernet and CompactFlash
®
Module
22
File Control utility in datalogger support software. Before collecting data this
way, stop the datalogger program to ensure data are not written to the CF card
while data are retrieved. Otherwise, data corruption and confusion will result.
7.4.1.1
Fast Storage/Data-Collection Constraints
When LoggerNet collects data from ring tables that have filled, there is the
possibility of missing records due to the collection process. LoggerNet uses a
“round-robin” collection algorithm that collects data from multiple tables in small
blocks as it sequences around to all the tables. Collection starts at the oldest data
for each table. When a ring table has filled, the oldest data is overwritten by
current data.
With filled ring tables, as collection begins LoggerNet queries the datalogger for
the oldest data starting with the first table. When this data block is returned,
LoggerNet goes to the next table and so on until all of the tables are initially
collected. By the time LoggerNet makes the second pass requesting more data
from the tables, the possibility exists that some of that data may have been
overwritten, depending on how fast the datalogger is storing data (that is, data
storage rate, number of table values, and number of tables).
Normally, LoggerNet gets ahead of the storing datalogger and the remaining data
is collected without gaps; however, if the datalogger is storing data fast enough, it
is possible to get into an always-behind scenario where LoggerNet never catches
up and the datalogger repeatedly overwrites uncollected data.
The possibility of missing records is greater when collecting data via IP. This is
due to the high demand of IP on processor time. The risk is greatest with a
CR1000 datalogger using IP, because of its slower processor speed relative to the
CR3000.
7.4.2
Transporting CF Card to Computer
With large files, transferring the CF card to a computer may be faster than
collecting the data over a link.
Removing a card while it is active can cause garbled data and
can actually damage the card. Do not switch off the
datalogger power if a card is present and active.
To remove a card, press the Initiate Removal button on the NL115. The
datalogger will transfer any buffered data to the card and then power off. The
Status LED will turn green when it is OK to remove the card. The card will be
reactivated after 20 seconds if it is not removed.
When the CF card is inserted into a computer, the data files can be copied to
another drive or used directly from the CF card just as one would from any other
disk. In most cases, however, it will be necessary to convert the file format before
using the data.
When dealing with large data files, it may be faster to use an
external card reader (such as pn #17752) rather than a PC card slot.
7.4.2.1
Converting File Formats
Files can be converted using LoggerNet’s CardConvert. Go to Data | CardConvert
and click on “Select Card Drive”. Select where the files to be converted are stored
and press OK. Next, click on “Change Output Dir” and select where you would
like the converted files to be stored. Place check marks next to the files to be
CAUTION
NOTE
